There is an experimantal pathfinder online now: http://the.earth.li/~noodles/pathfind.html.
There is also a perl script to trace signature paths.
The AT&T PathServer, which is a very usefull tool to find trust path in the Web of Trust of PGP is currently offline.
As I have been informed by Stuart Stubblebine (http://www.research.att.com/~stubblebine) this is due the new key format and due the job transition of Mike Reiter. Mike says:
I wouldn't say that PathServer will *never* go back online, but rather only that it is down for the indefinite future.
I offered my help to get it running again. So let's see what happens. If you are interessted about what's going on, just fill out this little form: